Our goal is to understand the organization and control of taste signaling i.e. how individual pathways involved in taste transduction function and interact with each other. In the longer term we would like to define the components and the organization required for taste responses and to help elucidate the logic of taste coding. Specifically we would like to know what receptors mediate sweet and bitter taste; how tastant specificity and taste discrimination are accomplished; what topographic organization exists the various taste buds and papillae; and how the information is transmitted and encoded in the afferent nerves. We have focused on the isolation and characterization of genes encoding sweet, amino acid and bitter taste receptors that can be used to mark the cells, define the corresponding signaling pathways, dissect receptor specificity, generate topographic maps, and trace the respective neuronal connectivity circuits. We have identified and characterized two families of G-protein coupled receptors, T1Rs and T2Rs, that are expressed in distinct subsets of taste receptor cells and that include functionally validated sweet, amino acid and bitter taste receptors. The critical next steps in defining the logic of sweet, amino acid and bitter taste coding are to examine the physiology and connectivity pathways of T1R- and T2R-expressing cells in the various taste buds, and to study the impact of genetic ablation, or knockouts, of the different cells and receptor combinations.